This invention relates to a drum-type classifier which is characterized by having water separation paddles disposed coaxially one subsequent to the other at the sand discharge end of the drum.
Although when classifying sand, separation into uniform particle sizes is necessary, decreasing the amount of mud remaining in the classified sand is also important in improving the quality of the sand since the above quantity of mud will influence the strength of the concrete produced using the sand.
For the purpose of improving the above quality, conventional classifiers have had various kinds of improvements in the water separation paddles. However, since the sand is scooped from muddy water, the removal of the mud in the classified sand cannot be thoroughly achieved.
The inventor of this application has already disclosed in U.S. Pat. No. 4,055,487 a rotary-type sand classifier which can efficiently classify the sand of desired particulate size distribution. However, this apparatus cannot achieve the sufficient removal of mud.
It is especially difficult to decrease the quantity of mud in the final product when minute sand particles must be classified from very muddy water.
Accordingly, it is an object of the present invention to provide a rotary drum-type sand classifier for resolving the aforementioned problems which is characterized by having two rows of water separation paddles disposed coaxially with one subsequent to the other at the rear of the rotary drum. In short, the mud component contained in the classified sand is drastically decreased by the combination of the first ring of water separation paddles which scoop the minute sand particles from water containing a relatively large quantity of mud and the second ring of separation paddles which are disposed subsequent to the above first separation paddles and which clean the classified sand with the water.
It is another object of the present invention to provide a rotary drum-type sand classifier having a plurality of the above sand discharging mechanisms in rows at the rear end of the rotary drum which can further facilitate the cleaning of the classified sand.